JPH02304049A - Preparation of r (+) -aminocarnitine and s (-) -aminocarnitine - Google Patents

Abstract

PURPOSE: To obtain the subject compounds by adding one enantiomer of α- methylbenzylamine to an inexpensive substance e.g. crotonobetaine obtained from e.g. D-carnitine to obtain two diastereomers, reducing them after separation and debenzylating them.

CONSTITUTION: Crotonobetaine chloride is reacted with benzyl alcohol to obtain crotonobetaine benzyl ester chloride. Next, an excess of R- or S-alpha- methylbenzylamine is reacted. Next, the obtained diastereomers are resolved by e.g. fractional crystallization. Further, the diastereomers are debenzylated immediately by catalytic reduction to remove the N- and O-benzyl groups and to thereby obtain R(+)- or S(-)-aminocarnitine chlorides in a single step. Finally, they are converted into the respective hydrochlorides by treatment with hydrochloric acid. Crotonobetaine can be easily obtained by the dehydration of D-carnitine.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to R(+)-aminocarnitine and 5(-)-
The present invention relates to a method for producing aminocarnitine.

[Configuration of the Invention] The present invention provides N-[5(-)-alpha-methylbenzyl]-R(+)-aminocarnidine chloride and N-[
A mixture of diastereoisomers consisting of each benzyl ester of S(~)-alpha-methylbenzyl]-8(-)-aminocarnitine chloride, or N-[R(+)-
A mixture of diastereoisomers consisting of each benzyl ester of alpha-methylbenzyl-R(+)-aminocarnidine chloride and N-[R(+)-alpha-methylbenzylco-S(-:ll-aminocarnitine chloride) chromatographic separation on silica gel or fractional crystallization, followed by debenzylation of the separated diastereoisomers to form R(+)-aminocarnitine chloride and S(-
)-aminocarnitine chloride.

[Prior art and problems to be solved by the invention] In recent years, acyl derivatives of aminocarnitine (■, R = H
) and certain aminocarnitines (■, R-acetyl, N-caproyl, valmitoyl) have been of great interest.

-3~ N　I-I　R For example, D. L. Zienkins O,j;bi0,W.

Griffiths describes the antiketotic and antihypoglycemic effects of the racemic compound (D), and U.S. Pat. No. 4.521432 (Takeda)
is an optically active derivative, the inner salt of (-)-N-acedelaminocarnitine ([α]P--, 7.

4°, c-1,] (20) (possible application in the treatment of diabetes (marked = 1). A similar effect is shown in (+ ) - Aminocarnitine chloride hydrochloride has already been described (
[α]3'-→・6.3', c=I,
IN AcOH).

Therefore, it was necessary to develop a method to produce the two enantiomers of aminocarnitine.

In reality, R(→-)-aminocarnitine chloride is R
(-)-N-Acedelaminocarnitine is isolated as a product by acid hydrolysis or during the cultivation of microorganisms of the genus Emericella or Asperigillus, or as described in the aforementioned U.S. Pat. No. 4,521,432 (Takeda) It is described that it can be obtained through a process.

Synthesis of R(+)- and SC-''-aminocarnitine chloride starting from L- and D-asparagine is described by Shinagawa, J. Med. Chem., Vol. 30, No. 1458.
(1987). However, this method is complicated. The process involves seven steps and uses particularly hazardous reagents such as diazomethane. Therefore, this method is not suitable for industrial production, and the only value is that the absolute configurations of (+)-aminocarnitine and (-)-aminocarnitine can be determined as R-aminocarnitine and S-aminocarnitine, respectively. It is something.

Italian patent application 47738/87 (E
Italian patent no. 12 corresponding to P application no. 287523
05758), R-aminocarnitine chloride and S-aminocarnitine chloride can also be obtained by separation of racemic mixtures of (±)-N-acetylaminocarnitine. However, in this case, the starting material (±)-N-acetylaminocarnitine, Jenkins, Journal of Biological Chemistry CJ, Biol, Chem.
.

) Vol. 260, p. 14748 (1985), it was synthesized by a more complicated five-step method starting from a uracil derivative.

The object of the present invention is to provide R(
An object of the present invention is to provide a method for producing +)-aminocarnitine and 5C-)-aminocarnitine.

゛[Means for solving the problem] Specifically, the method of the present invention can be used to inexpensively produce D-carnitine (L
- It is possible to produce two enantiomers in good yields using substances such as crotonobetaine, which is easily obtained by dehydration of (obtained as a by-product during the production of lunithine), as a starting material. It is something to do.

One of the two enantiomers of alpha-methylbenzylamine is added to the benzyl ester of crotonobetaine chloride. Since a new chiral center is formed and the addition is not stereospecific, two possible diastereoisomers are obtained. If R(+)-alpha-methylbenzylamine is used, N-[R(+)-alpha-methylbenzyl]-R(+)-aminocarnitine chloride and N-[R(10)-alpha The benzyl ester of -methylbenzyl S(-)-aminocarnitine chloride is obtained. When using S(-)-alpha-methylbenzylamine, N-[S(-)-alphamethylpenzylcolnitine chloride and N-[S(-)-alphamethylpenzylco-aminocarnitine chloride are used. A benzyl ester is obtained.

In either case, the diastereoisomers can be separated by fractional crystallization or silica gel chromatography. The separated diastereoisomers are then immediately stripped of their N- and 0-benzyl groups by catalytic reduction, yielding R(+)- or S(-)-aminocarnitine chloride in a single step. According to the method of the present invention, R
(10)-'l and S(-)-aminocarnitine chloride are produced by the following synthetic route (Table 1).

□ More specifically, the method of the present invention includes the following steps.

(a) reacting crotonobetaine chloride with an excess amount of benzyl alcohol in the presence of hydrogen chloride gas or an acid catalyst such as thionyl chloride, concentrating the resulting reaction solution and separating crotonobetaine benzyl ester chloride; b) From the reaction mixture obtained by reacting crotonobetaine benzyl ester chloride with an excess amount of R- or S-alpha-methylbenzylamine at 10°C-30°C for 12-48 hours and precipitating with an organic solvent. N-(alpha-methylbenzyl)-aminocarnitine benzyl ester chloride is separated by precipitation with an organic solvent such as ethyl ether or acetonitrile;

C) fractional crystallization of the diastereoisomer thus obtained, preferably with acetone or methyl ethyl ketone;
or silica gel using a gradient solvent of chloroform-methanol as eluent. Each stereoisomer is hydrogenolyzed,
Separating R(+)- and 5(-)-aminocarnitine chloride; e) converting the aminocarnitine enantiomer obtained in the previous step into the hydrochloride salt of chloride with hydrochloric acid;

The process of the present invention will be explained in detail with reference to the following examples, but is not limited thereto.

Manufacture of crotonobetaine benzyl ester chloride 54ml of benzyl alcohol was mixed with crotonobetaine (15ml).
g; 0.083 mol). The resulting mixture is 0
Cool to ℃. Thionyl chloride (35 ml; 0.495 mol) is slowly added to the mixture. The mixture is then kept at room temperature for 16 hours. The solution is then concentrated under vacuum to remove excess thionyl chloride.

The residue is washed with isopropanol, concentrated under vacuum and added to acetone. Keep the acetone solution at 4°C = 11- all day and night. A precipitate was formed (19 g; yield 84%),
This is filtered and dried. The analysis results showed that the obtained compound was the target compound.

TLC silica gel eluent: Chloroform: Methanol: Isopropyl alcohol: Ht Q' Acetic acid (42:28N:10:I0
)RF=0.7 NMRD, Oδ7,5 (51-I,s, aromatic)
Near, 2-6.3 (2H, m, Cl-1=cI-1)
;5.2(2tl,s.

-CHt-@);4-. 2(2H,d,N”-CHJ
:3゜0(9H,s,(CHa)3N+) Melting point -78-80℃ N-(alpha-methylbenzyl)-aminocarnitine benzyl ester chloride R(+)-alpha-methylbenzylamine (47ml)
; 0.37 mol) is added to crotonobetaine benzyl ester chloride (26 g; 0.096 mol). The resulting solution is kept at room temperature with stirring for 24 hours. Ethyl ether is added to the solution to obtain a precipitate (33 g; yield 87
．． 5%).

TLC silica gel eluent: chloroform-methanol (80-20) reaction crude product is N-(R(+)-alpha-methylbenzyl)-R(+)-aminocarnitine benzyl ester chloride, RF value (small) = 0 ．． e; and N −(R(+
)-alpha-methylbenzyl)-8(-)-aminocarnitine benzyl ester chloride, RF value (large) = 0
．． It is a mixture of two diastereoisomers of 8.

NMRD, Oδ 7.1 (IOH, doublet S.

Aromatic): 5, O(2H,s, CHv-■):
4.03,'8(2H,m, CHCH3;CHNH
): 3, 4 (2H, m, N''-CHt): 3,
2 (9H,s, (CH,)sN”); 2.-8(2H
, m, -CH,C00-); 1.2(3H,d, -CH
-C and. ) Separation of diastereoisomers The crude reaction product was dissolved in chloroform and passed through a silica gel column (ratio 1:20). Eluent, chloroforno, \-methanol (95-5) Product with RF value (low) that separated the following compounds: N-(R(+)-alpha-
methylbenzene)-1(+)-aminocarnitine hennol ester Cl:'i lido[α]55--12 (c=1.1120) Melting point 176
-178°C HPLC column Tecopac C11l eluent, solvent A -C1-11CN (58-42) (solvent Δ: methanol 100ml + 85% 11,, PO.

Detection UV 205nm Flow rate 1ml 17min Retention time: 6.69min Purity: 95% RF value (large) product・N-(R(+)-alpha) methylbenzyl)-3(-)-aminocarnitine pencil ester chloride [αli'+5-+52,6(c-],lI,o
) Melting point +60-62℃ HPLC: Same retention time as J- 8.28 minutes Purity: 90% Elemental analysis: (C7,4(3N2c]o2) 0% H%
N% C1% Theoretical value 67.58 7,99 7,16 9.
06 measurement value・67.52 8.02 7.09
9.13 Separation of diastereoisomers can also be achieved by recrystallization with methyl ethyl ketone, with RF' values (small)
The compound with a purity of 80% was obtained, and the compound with a high RF value remained in the mother liquor.

Step D R(+)-aminocarnitinc [7 Lito production step C I' (compound with F value (small), i.e., N-(R(+)
-alpha-methylbenzyl)-R(→-)-aminocarnidine henzyl ester (Ig; 0.0025 mol) in methanol-Tr, O (ratio 1:I) 10
Dissolve in ml. Pd(OH), 500
Add mg. The solution is hydrogenated at 4 atmospheres overnight.

The catalyst is then filtered off and the resulting sawdust solution is concentrated in vacuo. The residue is washed with isopropyltubanol and the resulting solid is filtered off. 0.5 g of crystalline material was obtained.

Yield: 100% [α], 15-1-12 (C=I, H7O) Melting point:
194°-] 996° C elementary analysis: (CJIr+N2Cl07) 0% 1
1% N% C1% Theoretical value 42,748.71 H, 2318,0
2 measurement value + 41.74 9.08 13.35
18.04 Step - Production of R(-1-)-aminocarnitine chloride hydrochloride For comparison with physical and chemical data of aminocarnitine chloride described in chemical literature, R(+)-aminocarnitine chloride was prepared at pH 1.8. 1-1Cl aqueous solution is added until the amount of 1-1 Cl is reached, and then freeze-dried. A solid product was obtained.

[α]o'-+ 7 (c-1, I-120) Melting point・2
10°-212°C Elemental analysis C71-1+ e N 2 C102C
% ) (% N% C1% theoretical value 36
, 06 7.78 +, 2.01 30.41 Measured value + 35.70 7.84 11.50 29
．． 78N M RD , Oδ 4 , 2(l H,m
-C几-);□ 3.8 (2H, d, N" CH2): 3.2 (91 (,
S, (C1(3)3N+-)+2.8(2H,d,-C
H2COO) HP L C: Column Micro Bondapak CNl Eluent KH2PO40,05M-CI (3
cN detection UV 205 nm Flow rate: I m 17 min Retention time, 2.0.3 min Identification of enantiomer of R(→-)-aminocarnitine chloride hydrochloride (excess) Aminocarnitine was determined as shown in Table 2. Excess anhydrous orthophthalaldehyde and acedercysteine were determined by the method used to identify amino acids in enantiomeric excess as described in Analytical Chemistry (Chem), Vol. 51 (II), p. 1667 (1979). was used to derive the derivative.

The mixture of derivatives was analyzed by HP L,C.

HPLC: Column Micro Bondapak 0IIl
Eluent: NaClO40,05M-CI (, CN detection U
V: 336 nm Flow rate: I ml/min 95%-R(+)-aminocarnidine retention time: I7.5 min 5%-8(-)-aminocarnidine retention time: 20.6 min Patent applicant Sigma-Tau Pharmaciu Tiche Industrie Socheta Bel Azioni

Claims (1)

[Claims] 1. A) Reacting crotonobetaine chloride with an excess amount of benzyl alcohol in the presence of an acid catalyst,
The resulting reaction solution was concentrated, thus separating the crotonobetaine benzyl ester chloride, and B) the crotonobetaine benzyl ester chloride was treated with excess R- or S-alpha-methylbenzylamine at 10°C-30°C for 12 hours. - reacting for 48 hours and separating N-(alpha-methylbenzyl)-aminocarnitine benzyl ester chloride from the resulting reaction mixture by precipitation with an organic solvent; C) resolving the diastereoisomers thus obtained; ) hydrogenolyzing each of the diastereoisomers in an aqueous alcoholic solution in the presence of a hydrogenation catalyst selected from the group consisting of palladium hydroxide and palladium chloride;
separating R(+)- and S(-)-aminocarnitine chloride; E) converting the aminocarnitine enantiomer obtained in the previous step into the hydrochloride salt of chloride with hydrochloric acid;
A method for producing (+)-aminocarnitine and S(-)-aminocarnitine. 2. The method according to claim 1, wherein the acid catalyst in step A) is selected from the group consisting of hydrogen chloride gas and thionyl chloride. 3. The method according to claim 1, wherein the organic solvent in step B) is selected from the group consisting of ethyl ether and acetonitrile. 4. The method according to claim 1, wherein the separation in step C) is carried out by fractional crystallization using acetone or methyl ethyl ketone. 5. The method of claim 1, wherein the resolution in step C) is carried out by chromatography on silica gel using a chloroform-methanol gradient as eluent. 6. A) Reacting crotonobetaine chloride with benzyl alcohol to obtain crotonobetaine benzyl ester chloride; B) Reacting crotonobetaine benzyl ester chloride with R-
or reaction with S-alpha-methylbenzylamine to separate the N-(alpha-methylbenzyl)-aminocarnitine benzyl ester chloride; C) resolution of the diastereoisomers thus obtained; D) metal for hydrogenation. In the presence of a catalyst, the diastereoisomers are hydrogenolyzed, R(+)- and S(-), respectively.
- A method for producing aminocarnitine.